DISCOGRAPHY AND EPIDUROGRAPHY FOR EVALUATION OF THE LUMBOSACRAL JUNCTION IN DOGS WITH CAUDA EQUINA SYNDROME

What is the evidence? The issue of verifying correct needle position during epidural anaesthesia in dogs

OBJECTIVES

To review the methods for verifying the needle position while performing epidural anaesthesia in dogs, and to discuss the advantages, disadvantages, usefulness and reliability of each technique in the experimental and clinical research setting.

DATABASES USED

PubMed, Scopus, Google Scholar and the Basel University Library online catalogues; the latter, which was provided by the University of Berne, were used as databases. The results were filtered manually based on the titles and abstracts in order to narrow the field.

CONCLUSIONS

Besides some drawbacks, including the potential side effects of contrast medium injection, which may limit its routine use in clinical patients, epidurography should still be regarded as one of the most reliable techniques to verify needle position in dogs. Ultrasonography, electrical nerve stimulation, loss of resistance and the hanging drop technique are regarded as less invasive than epidurography and, for this reason, their use may be more applicable to clinical patients. However, these methods have been described in only a few published reports, all of which involved a limited number of dogs. Finally, the detection of epidural pressure waves has been investigated more extensively in dogs, and the findings of these studies suggest that this technique may be used to verify epidural needle placement for experimental and clinical research, on condition that all the negative subjects are excluded from the study.

Transarticular facet screw stabilization and dorsal laminectomy in 26 dogs with degenerative lumbosacral stenosis with instability

OBJECTIVE

To describe outcome after transarticular facet screw stabilization and dorsal laminectomy for treatment of dynamic degenerative lumbosacral stenosis (DLS) in 26 dogs.

STUDY DESIGN

Retrospective case series.

ANIMALS

Dogs (n = 26) with dynamic DLS.

METHODS

Medical records (2004-2009) of dogs treated with transarticular facet screw stabilization and dorsal laminectomy were reviewed. Dogs (n = 26) were available for immediate postoperative follow-up, 21 dogs at 6 weeks, and 15 at greater than 6 months. Dogs were evaluated by radiographic assessment and owner questionnaire. Lumbosacral (LS) intervertebral disc (IVD) spaces were measured on pre and postoperative 6-week and 6-month radiographs.

RESULTS

In 23 dogs, improvement in clinical signs occurred within 7 days of surgery. Overall postsurgical complication rate directly related to the surgical procedure was 15.4%. LS IVD space measurements taken immediately postoperatively, at 6 weeks, and ≥ 6 months were all significantly increased compared with preoperative measurements. All working dogs (4) returned to full work within 14 months. Most owners (85%) reported their dog was ambulating normally at 6 months with no perceptible lameness during normal activity. All owners perceived their dog's ability to walk, run, and jump after surgery to be improved.

CONCLUSIONS

Transarticular facet screw stabilization and dorsal laminectomy maintains distraction of the LS IVD space for medium-to-large breed dogs with dynamic DLS with a high degree of owner satisfaction, and is comparable to other reported surgical techniques for DLS.

Asymmetrical, Transitional, Lumbosacral Vertebral Segments in Six Dogs: A Characteristic Spinal Syndrome

Clinical findings in six dogs with asymmetrical, transitional, lumbosacral vertebral segments are reported. All dogs exhibited low back pain and varying degrees of asymmetrical cauda equina dysfunction. Results of myelography, epidurography, and magnetic resonance imaging (MRI) indicated a unilateral disk protrusion in all dogs. In the dogs with MRIs, focal degenerative alterations in the vertebral end plates and adjacent body of the vertebra were detected. All dogs were treated with a dorsal laminectomy or hemilaminectomy. Results following surgery were good or excellent in all six dogs.

Computed tomography of the normal lumbosacral intervertebral disc in 22 dogs

Computed tomography of the lumbosacral spine was performed on 22 purpose-bred, medium-sized hound dogs between 1 and 6 years of age. Images were evaluated to determine the degree of disc bulge. All dogs were neurologically normal. Dogs were imaged in dorsal recumbency with the pelvic limbs variably extended. Sagittal reconstructions were made from transverse images. The mean (+/-SD) width of the mid-portion of the L7-S1 intervertebral disc was 0.5 +/- 0.07 cm (range 0.33-0.62 cm). All L7-S1 intervertebral discs were dorsally convex, with the mean bulge measuring 0.25 +/- 0.07 cm (range 0.17-0.50 cm). The height of the vertebral canal at L7-S1 was 0.91 +/- 0.11 cm (range 0.68-1.15 cm). The mean percentage of the vertebral canal occupied by the bulge was 26.89 +/- 5.05% (range 20.74-43.08%). Mild bulging of the L7-S1 intervertebral disc can be present without associated neuropathy in medium-sized dogs.

Association of cauda equina compression on magnetic resonance images and clinical signs in dogs with degenerative lumbosacral stenosis

Magnetic resonance imaging (MRI) was used to examine the lumbosacral spine of 27 dogs with degenerative lumbosacral stenosis. Four normal dogs were also similarly imaged. Compression of the soft-tissue structures within the vertebral canal at the lumbosacral space was assessed in two ways: by measuring dorsoventral diameter on T1-weighted sagittal images and cross-sectional area on transverse images. The severity of the clinical signs was compared to the severity of cauda equina compression. No significant correlation was found. It is concluded that degree of compression as determined by MRI at time of presentation is independent of disease severity.

Predictors of outcome after dorsal decompressive laminectomy for degenerative lumbosacral stenosis in dogs: 69 cases (1987-1997)

OBJECTIVE

To identify predictive factors of long-term outcome after dorsal decompressive laminectomy for the treatment of degenerative lumbosacral stenosis (DLSS) in dogs.

DESIGN

Retrospective study.

SAMPLE POPULATION

69 client-owned dogs.

PROCEDURE

Medical records of dogs that had undergone dorsal laminectomy at North Carolina State University and the University of Tennessee between 1987 and 1997 were reviewed. Dogs with diskospondylitis, traumatic lesions, or neoplasia of the lumbosacral region were excluded. All dogs had evidence of cauda equina compression on myelography, epidurography, computed tomography, or magnetic resonance imaging, along with subsequent confirmation of the lesion at surgery. Follow-up was performed by telephone inquiries to the referring veterinarian, the owner, or both, using a detailed questionnaire.

RESULTS

The outcome was excellent or good in 54 of 69 (78%) dogs over a mean follow-up period of 38+/-22 months. Five of these 54 dogs had been incontinent for a median of 2 weeks prior to surgery. Six of the 15 dogs with a poor outcome had been incontinent for a median of 8 weeks before surgery. A significant correlation was detected between the presence of urinary and fecal incontinence prior to surgery and outcome. When duration of signs was considered, urinary incontinence was the only variable that significantly affected outcome.

CONCLUSIONS AND CLINICAL RELEVANCE

Decompressive laminectomy is an effective treatment for DLSS, although dogs with urinary or fecal incontinence have a worse prognosis than dogs that are continent before surgery. Chronic urinary incontinence is a predictor of poor outcome for dogs with DLSS.

Cauda equina syndrome

Single or double-level compression of the lumbosacral nerve roots located in the dural sac results in a polyradicular symptomatology clinically diagnosed as cauda equina syndrome. The cauda equina nerve roots provide the sensory and motor innervation of most of the lower extremities, the pelvic floor and the sphincters. Therefore, in a fully developed cauda equina syndrome, multiple signs of sensory disorders may appear. These disorders include low-back pain, saddle anesthesia, bilateral sciatica, then motor weakness of the lower extremities or chronic paraplegia and, bladder dysfunction. Multiple etiologies can cause the cauda equina syndrome. Among them, non-neoplastic compressive etiologies such as herniated lumbosacral discs and spinal stenosis and spinal neoplasms play a significant role in the development of the cauda equina syndrome. Non-compressive etiologies of the cauda equina syndrome include ischemic insults, inflammatory conditions, spinal arachnoiditis and other infectious etiologies. The use of canine, porcine and rat models mimicking the cauda equina syndrome enabled discovery of the effects of the compression on nerve root neural and vascular anatomy, the impairment of impulse propagation and the changes of the neurotransmitters in the spinal cord after compression of cauda equina. The involvement of intrinsic spinal cord neurons in the compression-induced cauda equina syndrome includes anterograde, retrograde and transneuronal degeneration in the lumbosacral segments. Prominent changes of NADPH diaphorase exhibiting, Fos-like immunoreactive and heat shock protein HSP72 were detected in the lumbosacral segments in a short-and long-lasting compression of the cauda equina in the dog. Developments in the diagnosis and treatment of patients with back pain, sciatica and with a herniated lumbar disc are mentioned, including many treatment options available.

Degenerative lumbosacral stenosis

This article reviews the management of degenerative lumbosacral stenosis. Degenerative lumbosacral stenosis occurs when soft tissue and bony changes, possibly in conjunction with abnormal motion of the lumbosacral joint, impinge on the nerve roots or vasculature of the cauda equina. It occurs most frequently in middle-aged dogs of medium to large breed, especially the German Shepherd dog. Common signs are lumbosacral pain, lameness, pelvic limb weakness and ataxia, and urinary incontinence. Diagnosis is based on clinical features and imaging studies. Decompressive surgery is effective in most patients.

Transitional lumbosacral vertebral anomaly in the dog: a radiographic study

Transitional lumbosacral vertebral anomalies have for some time been suggested as a possible cause of cauda equina syndrome (especially in the German shepherd dog [GSD]), a condition recently thought to be inherited. The frequency of this condition within a large clinical population and the radiographic features used in its detection are reported. In a group of 143 patients, the sexes were similarly represented and the GSD was greatly overrepresented. The anomaly is characterised by separation of the first sacral segment that was identified on the lateral view by the presence of a radiolucent disc space between what are normally the first and second sacral segments. On the ventrodorsal view, the anomaly was characterised by separation of the spinous processes between what are normally the first and second sacral segments. In the presence of the transitional segment, the nature of the sacroiliac joint at the level of the anomalous segment varies from a strong ilial attachment, with the presence of a wing-like lateral process, to a weakened ilial attachment because of the presence of a lateral process, shaped as that seen on a lumbar segment. These patterns were present unilaterally or bilaterally and result in symmetrical or asymmetrical patterns. The effect of the weakening of the sacroiliac attachment was thought to result in premature disc degeneration, which, together with spinal canal stenosis, resulted in potential compression of the overlying spinal nerves and creation of a cauda equina syndrome. The condition is thought to have clinical significance and should be selected against in breeding, especially in the GSD.

A review of imaging techniques for canine cauda equina syndrome

There are many imaging modalities available for evaluating the canine lumbosacral region. These include conventional radiography, stress radiography, myelography, epidurography, transosseous and intravenous venography, discography, linear tomography, computed tomography, and magnetic resonance imaging. Myelography, epidurography and discography are commonly used, but often lack sensitivity. Myelography is of little value when evaluating the cauda equina because the dural sac is elevated from the vertebral canal floor and frequently ends before the lumbosacral junction. Epidurography will identify a ventrally located compressive lesion and discography can delineate the dorsal extent of the diseased disc; however, both are sometimes difficult to interpret. Therefore, more than one of these imaging techniques must be used in order to make a diagnosis. Computed tomography and magnetic resonance imaging have become valuable in evaluating the lumbosacral region in dogs. These modalities have proven to be both sensitive and specific for determining cauda equina compression in both humans and in dogs.

Fluoroscopically guided percutaneous disk aspiration in 10 dogs with diskospondylitis

Fluoroscopically guided percutaneous fine-needle aspiration of the intervertebral disk space was performed in 10 dogs with diskospondylitis. Positive bacterial cultures were obtained from 9 of 12 aspirated disk spaces, 1 of 6 blood cultures, and 6 of 10 urine cultures. Positive disk cultures were obtained from 2 dogs with negative blood and urine cultures and from 2 additional dogs with low numbers of Staphylococcus in urine cultures. Adverse clinical sequelae of the procedure were not noted. Percutaneous fine-needle aspiration of the intervertebral disk space is an alternative technique to surgical biopsy to obtain positive bacterial cultures from dogs with diskospondylitis.